import React, { Component } from 'react'
import PropTypes from 'prop-types'

import './index.css'

export default class Header extends Component {

    //对接收的props进行类型、必要性的限制
    static propTypes = {
        addTodo: PropTypes.func.isRequired
    }

    //键盘事件的回调
    handleKeyUp = (event) => {
        //判断是否是回车按键
        if(event.keyCode !== 13) 
            return;
        //添加的todo名字不能为空
        if(event.target.value.trim() === '') {
            alert('输入不能为空');
            return;
        }
        //传输输入值
        this.props.addTodo(event.target.value);
        //清空输入值
        event.target.value = '';
    }

    render() {
        return (
            <div>
                <div className="todo-header">
                    <input onKeyUp={this.handleKeyUp} type="text" placeholder="请输入你的任务名称，按回车键确认"/>
                </div>
            </div>
        )
    }
}
